Structural descriptions for neurosynaptic networks

ABSTRACT

Embodiments of the invention provide a method comprising creating a structural description for at least one neurosynaptic core circuit. Each core circuit comprises an interconnect network including plural electronic synapses for interconnecting one or more electronic neurons with one or more electronic axons. The structural description defines a desired neuronal activity for the core circuits. The desired neuronal activity is simulated by programming the core circuits with the structural description. The structural description controls routing of neuronal firing events for the core circuits.

This invention was made with Government support under HR0011-09-C-0002awarded by Defense Advanced Research Projects Agency (DARPA). TheGovernment has certain rights in this invention.

BACKGROUND

The present invention relates to neuromorphic and synaptroniccomputation, and in particular, structural descriptions forneurosynaptic networks.

Neuromorphic and synaptronic computation, also referred to as artificialneural networks, are computational systems that permit electronicsystems to essentially function in a manner analogous to that ofbiological brains. Neuromorphic and synaptronic computation do notgenerally utilize the traditional digital model of manipulating 0s and1s. Instead, neuromorphic and synaptronic computation create connectionsbetween processing elements that are roughly functionally equivalent toneurons of a biological brain. Neuromorphic and synaptronic computationmay comprise various electronic circuits that are modeled on biologicalneurons.

In biological systems, the point of contact between an axon of a neuralmodule and a dendrite on another neuron is called a synapse, and withrespect to the synapse, the two neurons are respectively calledpre-synaptic and post-synaptic. The essence of our individualexperiences is stored in conductance of the synapses. The synapticconductance changes with time as a function of the relative spike timesof pre-synaptic and post-synaptic neurons, as per spike-timing dependentplasticity (STDP). The STDP rule increases the conductance of a synapseif its post-synaptic neuron fires after its pre-synaptic neuron fires,and decreases the conductance of a synapse if the order of the twofirings is reversed.

BRIEF SUMMARY

In one embodiment, the present invention provides a method comprisingcreating a structural description for at least one neurosynaptic corecircuit. Each core circuit comprises an interconnect network includingplural electronic synapses for interconnecting one or more electronicneurons with one or more electronic axons. The structural descriptiondefines a desired neuronal activity for the core circuits. The desiredneuronal activity is simulated by programming the core circuits with thestructural description. The structural description controls routing ofneuronal firing events for the core circuits.

Another embodiment comprises a framework including at least onestructural description for programming a neural network includingmultiple interconnected neural core circuits, wherein each core circuitcomprises an interconnect network including plural electronic synapsesfor interconnecting one or more electronic neurons with one or moreelectronic axons. Each structural description defines a desired neuronalactivity for at least one core circuit of the neural network. Eachstructural description controls the routing of neuronal firing eventspropagating through the neural network.

These and other features, aspects, and advantages of the presentinvention will become understood with reference to the followingdescription, appended claims, and accompanying figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an example core circuit, in accordance with anembodiment of the invention;

FIG. 2 illustrates an example neural network circuit including multipleinterconnected core circuits, in accordance with an embodiment of theinvention;

FIG. 3 illustrates a high-level block diagram of the neural networkcircuit in FIG. 2, in accordance with an embodiment of the invention;

FIG. 4 illustrates a corelet for at least one core circuit, inaccordance with an embodiment of the invention;

FIG. 5 illustrates an example corelet for three core circuits, inaccordance with an embodiment of the invention;

FIG. 6 illustrates a hierarchical composition of corelets, in accordancewith an embodiment of the invention;

FIG. 7 illustrates a complex corelet for multiple corelets, inaccordance with an embodiment of the invention;

FIG. 8 illustrates an example complex corelet composed from twocorelets, in accordance with an embodiment of the invention;

FIG. 9 is a high-level block diagram illustrating a framework forcomposing, decomposing, and maintaining corelets, in accordance with anembodiment of the invention;

FIG. 10 illustrates an example input mapping table, in accordance withan embodiment of the invention;

FIG. 11 illustrates an example output mapping table, in accordance withan embodiment of the invention;

FIG. 12 illustrates a flowchart of an example process for programming aneural network, in accordance with an embodiment of the invention; and

FIG. 13 illustrates a high-level block diagram showing an informationprocessing system useful for implementing one embodiment of the presentinvention.

DETAILED DESCRIPTION

The present invention relates to neuromorphic and synaptroniccomputation, and in one embodiment, the present invention provides amethod comprising creating a structural description for at least oneneurosynaptic core circuit. Each core circuit comprises an interconnectnetwork including plural electronic synapses for interconnecting one ormore electronic neurons with one or more electronic axons. Thestructural description defines a desired neuronal activity for the corecircuits. The desired neuronal activity is simulated by programming thecore circuits with the structural description. The structuraldescription controls routing of neuronal firing events for the corecircuits.

Another embodiment comprises a framework including at least onestructural description for programming a neural network includingmultiple interconnected neural core circuits, wherein each core circuitcomprises an interconnect network including plural electronic synapsesfor interconnecting one or more electronic neurons with one or moreelectronic axons. Each structural description defines a desired neuronalactivity for at least one core circuit of the neural network. Eachstructural description controls the routing of neuronal firing eventspropagating through the neural network.

Each corelet comprises at least one constituent unit, wherein eachconstituent unit corresponds to one of the following: a portion of acore circuit, a core circuit, or another structural description.

Each structural description further defines an input mapping tableincluding routing information for each input received by at least onecorresponding core circuit, wherein, based on the input mapping table,each input received is mapped to an input of a constituent unit. Aninput of a constituent unit is an axon or an input of another structuraldescription. Each input received by at least one corresponding corecircuit is one of the following: an incoming neuronal firing event, or asensory input from a sensory unit.

Each structural description further defines an output mapping tableincluding routing information for each output generated by eachconstituent unit, wherein, based on the output mapping table, eachoutput generated by each constituent unit is mapped to one of thefollowing: an input of a constituent unit, or an output of at least onecorresponding core circuit. An output of at least one corresponding corecircuit is routed to one of the following: another structuraldescription, or a motor unit. Each output generated by each constituentunit is an outgoing neuronal firing event.

A composer is configured to compose a structural description for one ormore core circuits. Composing a structural description comprisesspecifying a number of constituent units, assigning an identifier toeach constituent unit, mapping each input received by the one or morecore circuits, and mapping each output generated by each constituentunit. Each input received is mapped to an input of a constituent unit.Each output generated is mapped to one of the following: an input of aconstituent unit, or an output of the one or more corresponding corecircuits.

A library maintains a collection of structural descriptions fordifferent types of core circuits.

A decomposer is configured to decompose a structural description into aset of interconnected core circuits. Decomposing a structuraldescription into a set of interconnected core circuits compriseshierarchically decomposing the structural description by replacing alevel of indirection at each hierarchal level of the structuraldescription, and generating a corresponding flat data file includinginformation relating to the set of interconnected core circuits.

In one embodiment, the inputs received by the at least one core circuitare grouped into multiple groups of inputs, wherein each group comprisesat least one input. The outputs generated by the at least one corecircuit are grouped into multiple groups of outputs, wherein each groupcomprises at least one output. A group of outputs from the at least onecore circuit is mapped to a group of inputs targeting one or more corecircuits.

The term electronic neuron as used herein represents an architectureconfigured to simulate a biological neuron. An electronic neuron createsconnections between processing elements that are roughly functionallyequivalent to neurons of a biological brain. As such, a neuromorphic andsynaptronic computation comprising electronic neurons according toembodiments of the invention may include various electronic circuitsthat are modeled on biological neurons. Further, a neuromorphic andsynaptronic computation comprising electronic neurons according toembodiments of the invention may include various processing elements(including computer simulations) that are modeled on biological neurons.Although certain illustrative embodiments of the invention are describedherein using electronic neurons comprising electronic circuits, thepresent invention is not limited to electronic circuits. A neuromorphicand synaptronic computation according to embodiments of the inventioncan be implemented as a neuromorphic and synaptronic architecturecomprising circuitry, and additionally as a computer simulation. Indeed,embodiments of the invention can take the form of an entirely hardwareembodiment, an entirely software embodiment or an embodiment containingboth hardware and software elements.

FIG. 1 illustrates an example core circuit 10, in accordance with anembodiment of the invention. The core circuit 10 comprises a pluralityof electronic neurons 11 and a plurality of electronic incoming axons15. The neurons 11 and the incoming axons 15 are interconnected via anm×n crossbar 12 comprising multiple electronic synapse devices(“synapses”) 31, wherein m and n are integers greater than or equal toone. Each synapse 31 interconnects an incoming axon 15 to a neuron 11,wherein, with respect to the synapse 31, the incoming axon 15 and theneuron 11 represent an axon of a pre-synaptic neuron and a dendrite of apost-synaptic neuron, respectively.

Each neuron 11 receives firing events via interconnected incoming axons15 and, in response to the firing events received, generates a firingevent according to a neuronal activation function. For each neuron 11,the firing event generated by said neuron 11 propagates along acorresponding outgoing axon 13 of said neuron 11. A preferred embodimentfor the neuronal activation function can be leaky integrate-and-fire.

In one embodiment of the invention, when neurons 11 generate a firingevent, they maintain a postsynaptic-STDP (post-STDP) variable thatdecays. For example, in one embodiment, the decay period may be 50 ms.The post-STDP variable is used to achieve STDP by encoding the timesince the last firing of an associated neuron 11. Such STDP is used tocontrol long-term potentiation or “potentiation”, which in this contextis defined as increasing synaptic conductance. When incoming axons 15generate a firing event, they maintain a presynaptic-STDP (pre-STDP)variable that decays in a similar fashion as that of neurons 11.

Pre-STDP and post-STDP variables may decay according to exponential,linear, polynomial, or quadratic functions, for example. In anotherembodiment of the invention, variables may increase instead of decreaseover time. In any event, a variable may be used to achieve STDP byencoding the time since the last firing of an associated neuron 11. STDPis used to control long-term depression or “depression”, which in thiscontext is defined as decreasing synaptic conductance. Note that theroles of pre-STDP and post-STDP variables can be reversed with pre-STDPimplementing potentiation and post-STDP implementing depression.

An external two-way communication environment may supply sensory inputsand consume motor outputs. The neurons 11 and incoming axons 15 areimplemented using complementary metal-oxide semiconductor (CMOS) logicgates that receive firing events and generate a firing event accordingto the neuronal activation function. In one embodiment, the neurons 11and incoming axons 15 include comparator circuits that generate firingevents according to the neuronal activation function. In one embodiment,the synapses 31 are implemented using one-bit static random-accessmemory (SRAM) cells. Neurons 11 that generate a firing event areselected one at a time, and the firing events are delivered to targetincoming axons 15, wherein the target incoming axons 15 may reside inthe same core circuit 10 or somewhere else in a larger system with manycore circuits 10.

As shown in FIG. 1, the core circuit 10 further comprises anaddress-event receiver (Core-to-Axon) 4, an address-event transmitter(Neuron-to-Core) 5, and a controller 6 that functions as a global statemachine (GSM). The address-event receiver 4 receives firing events andtransmits them to target incoming axons 15. The address-eventtransmitter 5 transmits firing events generated by the neurons 11 to thecore circuits 10 including the target incoming axons 15.

The controller 6 sequences event activity within a time-step. Thecontroller 6 divides each time-step into operational phases in the corecircuit 10 for neuron updates, etc. In one embodiment, within atime-step, multiple neuron updates and synapse updates are sequentiallyhandled in a read phase and a write phase, respectively. Further,variable time-steps may be utilized wherein the start of a nexttime-step may be triggered using handshaking signals whenever theneuron/synapse operation of the previous time-step is completed. Forexternal communication, pipelining may be utilized wherein load inputs,neuron/synapse operation, and send outputs are pipelined (thiseffectively hides the input/output operating latency).

As shown in FIG. 1, the core circuit 10 further comprises a routingfabric 70. The routing fabric 70 is configured to selectively routeneuronal firing events among core circuits 10. The routing fabric 70comprises a firing events address lookup table (LUT) module 57, a packetbuilder (PB) module 58, a head delete (HD) module 53, and a core-to-corepacket switch (PSw) 55. The LUT 57 is an N address routing table isconfigured to determine target incoming axons 15 for firing eventsgenerated by the neurons 11 in the core circuit 10. The target incomingaxons 15 may be incoming axons 15 in the same core circuit 10 or othercore circuits 10. The LUT 57 retrieves information such as targetdistance, direction, addresses, and delivery times (e.g., about 19bits/packet×4 packets/neuron). The LUT 57 converts firing eventsgenerated by the neurons 11 into forwarding addresses of the targetincoming axons 15.

The PB 58 packetizes the routing information retrieved by the LUT 57into outgoing address-event router packets. The core-to-core PSw 55 isan up-down-left-right mesh router configured to direct the outgoingaddress-event router packets to the core circuits 10 containing thetarget incoming axons 15. The core-to-core PSw 55 is also configured toreceive incoming address-event router packets from the core circuits 10.The HD 53 removes routing information from an incoming address-eventrouter packet to deliver it as a time-stamped firing event to theaddress-event receiver 4.

FIG. 2 illustrates a neural network circuit 60 including multipleinterconnected core circuits 10, in accordance with an embodiment of theinvention. The core circuits 10 are arranged in a 6×8 array. Each corecircuit 10 may be identified by its Cartesian coordinates as core (i,j), where i is a column index and j is a row index in the array (i.e.,core (0,0), core (0,1), . . . , core (5,7)). Each synapse 31 and neuron11 have configurable operational parameters.

Each core circuit 10 utilizes its core-to-core PSw 55 (FIG. 1) to passalong neuronal firing events in the eastbound, westbound, northbound, orsouthbound direction. For example, a neuron 11 (FIG. 1) in the corecircuit (0,0) may generate a firing event for routing to a targetincoming axon 15 (FIG. 1) in the core circuit (5,7). To reach the corecircuit (5,7), the firing event may traverse seven core circuits 10 inthe eastbound direction (i.e., from core (0,0) to cores (0,1), (0,2),(0,3), (0,4), (0,5), (0,6), and (0,7)), and five core circuits 10 in thesouthbound direction (i.e., from core (0,7) to cores (1, 7), (2, 7), (3,7), (4, 7), and (5, 7)) via the core-to-core PSws 55 in the neuralnetwork 60.

FIG. 3 illustrates a high-level block diagram of the neural networkcircuit 60 in FIG. 2, in accordance with an embodiment of an invention.In one embodiment, the neural network circuit 60 is implemented using atleast one multi-core circuit chip structure 240. Each chip structure 240comprises multiple interconnected core circuits 10 (FIG. 2).

Each chip structure 240 may be programmed using a corelet 100 (FIG. 4).As described in detail later herein, a corelet 100 is a structuraldescription of one or more core circuits 10. In one embodiment, acorelet 100 is a static configuration file for programming a portion(i.e., a fraction) of a core circuit 10, a core circuit 10, or at leasttwo corelets 100 representing multiple interconnected core circuits 10.

Each chip structure 240 includes a memory unit 241. In one embodiment, acorelet 100 may be pre-loaded into the memory unit 241 of the chipstructure 240.

As shown in FIG. 3, the neural network circuit 60 may be connected toexternal spiking systems such as sensory units 220 and motor units 230.A sensory unit 220 represents a sensory transducer configured to providesensory input to the neural network circuit 60. In one embodiment, eachsensor input is propagated to a target incoming axon 15 of the neuralnetwork circuit 60 as a firing event.

A motor unit 230 represents a motor control system configured to providemotor output. A motor unit 230 may generate motor output in response tofiring events generated by one or more neurons 11 of the neural networkcircuit 60.

FIG. 4 illustrates a corelet 100 for at least one core circuit 10, inaccordance with an embodiment of the invention. Corelets 100 areapplicable to different types of neural core circuits. In oneembodiment, a corelet 100 is a static configuration file for programminga portion (i.e., a fraction) of a core circuit 10 or a core circuit 10.Corelets 100 may also be composed in a hierarchical fashion, such that acorelet 100 may be used to program two or more corelets 100 representingmultiple interconnected core circuits 10.

A corelet 100 may program the neuronal activity of a core circuit 10 ofthe neural network circuit 60. For example, a corelet 100 may be used toprogram the routing fabric 70 of each core circuit 10 of a chipstructure 240. Other examples of activities a corelet 100 may program acore circuit 10 to perform include edge detection in image/video, motionhistory tracking in video, object classification, sense-response in arobotic environment, and sound filtering.

Each corelet 100 comprises C constituent units (“constituentsub-corelets”) 110, wherein C is an integer greater than or equal toone. Each sub-corelet 110 defines one of the following: a portion (i.e.,a fraction) of a core circuit 10, a core circuit 10, or a corelet 100that in turn defines multiple interconnected core circuits 10. Forexample, each sub-corelet 110 in FIG. 4 is a core circuit 10. As anotherexample, each sub-corelet 110 in FIG. 6 is a corelet 100.

All sub-corelets 110 of the corelet 100 are numbered. For example, eachsub-corelet 110 may be identified by a corresponding index SC_(i),wherein 0≤i≤C−1.

The corelet 100 receives I inputs 120, wherein I is an integer greaterthan or equal to one. Each input 120 may represent a firing event fromanother corelet 100 or a sensory input from a sensory unit 220. Allinputs 120 received by the corelet 100 are addressed. For example, eachinput 120 may be addressed by a corresponding index Input_(j), wherein0≤j≤I−1.

The corelet 100 generates O outputs 130, wherein O is an integer greaterthan or equal to one. Each output 130 may represent a firing eventgenerated by a neuron 11 of a sub-corelet 110. Each output 130 may berouted to another corelet 100 or a motor unit 230. All outputs 130generated by the corelet 100 are addressed. For example, each output 130may be addressed by a corresponding index Output_(k), wherein 0≤k≤O−1.

The corelet 100 further comprises an input mapping table 140 and anoutput mapping table 150. In one embodiment, each table 140, 150 is arouting table that maintains routing information. As described in detaillater herein, the input mapping table 140 maintains routing informationfor each input 120 received by the corelet 100. Based on the inputmapping table 140, each received input 120 is mapped to an input of asub-corelet 110 within the corelet 100. If each sub-corelet 110 is acore circuit 10, each received input 120 is mapped to a target incomingaxon 15. If each sub-corelet 110 is a corelet 100, each received input120 is mapped to an input 120 of a corelet 100.

As described in detail later herein, the output mapping table 150maintains routing information for each output generated by eachsub-corelet 110 of the corelet 100. If a sub-corelet 110 is a corecircuit 10, the output generated by the sub-corelet 110 is a firingevent. If a sub-corelet 110 is a corelet 100, the output generated bythe sub-corelet 110 is an output 130. Based on the output mapping table150, each output generated by a sub-corelet 110 is mapped to one of thefollowing: an input of a sub-corelet 110 within the corelet 100 (e.g., atarget incoming axon 15, or an input 120 of a corelet 100), or an output130 of the corelet 100. As stated above, each output 130 is routed toanother corelet 100 or a motor unit 230.

FIG. 5 illustrates an example corelet 100 for three core circuits 10, inaccordance with an embodiment of the invention. As shown in FIG. 3, thecorelet 100 comprises three sub-corelets 110, wherein each sub-corelet110 is a core circuit 10. In one embodiment, each core circuit 10comprises a 256×256 ultra-dense crossbar 12 (FIG. 1) of synapses 31(FIG. 1) that interconnects 256 neurons 11 (FIG. 1) with 256 incomingaxons 15 (FIG. 1).

At maximum, the corelet 100 in FIG. 5 has about 768 (i.e., 256×3) inputs120 (FIG. 4) and about 768 (i.e., 256×3) outputs 130 (FIG. 4). Thenumber of inputs 120 and the number of outputs 130 may be less,depending on the interconnections between the sub-corelets 110 asdetermined by the input mapping table 140 (FIG. 4) and the outputmapping table 150 (FIG. 4).

FIG. 6 illustrates a hierarchical composition of corelets 100, inaccordance with an embodiment of the invention. Each corelet 100 ismodular, reusable, and scalable. Corelets 100 may be combined to form acorelet 100. In one embodiment, a complex corelet 160 is a corelet 100that is composed of at least two corelets 100. Complex corelets 160 areused to program multiple corelets 100 representing multipleinterconnected core circuits 10.

FIG. 7 illustrates a complex corelet 160 for multiple corelets 100, inaccordance with an embodiment of the invention. In one embodiment, acomplex corelet 160 is composition of C corelets 100, wherein C isgreater than or equal to 2. Each corelet 100 of the complex corelet 160is a sub-corelet 110 of the complex corelet 160. All sub-corelets 110 ofthe complex corelet 160 are numbered. For example, each sub-corelet 110may be identified by a corresponding index SC_(i), wherein 0≤i≤C−1.

As stated above, a complex corelet 160 is a corelet 100. Therefore, thecomplex corelet 160 receives I inputs 120, and generates O outputs 130,wherein I and O are integers greater than or equal to one. The complexcorelet 160 further comprises an input mapping table 140 and an outputmapping table 150. Based on the input mapping table 140, each receivedinput 120 is mapped to an input 120 of a corelet 100 within the complexcorelet 160. Based on the output mapping table 150, each output 130generated by a corelet 100 within the complex corelet 160 is mapped toone of the following: an input 120 of a corelet 100 within the complexcorelet 160, or an output 130 of the complex corelet 160.

FIG. 8 illustrates an example complex corelet 160 composed from twocorelets 100, in accordance with an embodiment of the invention. Asshown in FIG. 8, the complex corelet 160 has two sub-corelets 110,wherein each sub-corelet 110 is a corelet 100. Specifically, the corelet160 in FIG. 8 is composed of a first corelet 100 (Corelet A) and asecond corelet 100 (Corelet B).

The first corelet 100 is configured for programming three interconnectedcore circuits 10. The second corelet 100 is configured for programmingtwo interconnected core circuits 10. Therefore, the complex corelet 160is configured for programming five interconnected core circuits 10.

In one embodiment, each core circuit 10 comprises a 256×256 ultra-densecrossbar 12 (FIG. 1) of synapses 31 (FIG. 1) that interconnect 256neurons 11 (FIG. 1) with 256 incoming axons 15 (FIG. 1). At maximum, thefirst corelet 100 can have about 768 (i.e., 256×3) inputs 120 (FIG. 4)and about 768 (i.e., 256×3) outputs 130 (FIG. 4), and the second corelet100 can have about 512 (i.e., 256×2) inputs 120 and about 512 (i.e.,256×2) outputs 130. Therefore, at maximum, the complex corelet 160 canhave about 1280 (i.e., 256×5) inputs 120 and about 1280 (i.e., 256×5)outputs 130. The number of inputs 120 received by, and the number oroutputs 130 generated by, the complex corelet 160 may be less, dependingon the interconnections between the sub-corelets 110 as determined bythe input mapping table 140 (FIG. 4) and the output mapping table 150(FIG. 4).

FIG. 9 is a high-level block diagram illustrating a framework 200 forcomposing, decomposing, and maintaining corelets 100 (FIG. 4), inaccordance with an embodiment of the invention. The framework 200comprises a corelet library 210, a corelet composer 205, and a coreletdecomposer 215. The corelet library 210 maintains an ever-growingcollection of corelets 100. Each corelet 100 maintained in the coreletlibrary 210 has corresponding documentation providing informationrelating to the inputs 120 received by the corelet 100, the outputs 130generated by the corelet 100, the function of the corelet 100, and thecost of utilizing the corelet 100 to program a portion of a neuralnetwork circuit 60.

The corelet composer 205 is configured for composing complex corelets160. The corelet decomposer 215 is configured fordecomposing/deconstructing a corelet 100, and generating a correspondingdata file that provides information relating to a set of interconnectedcore circuits 10 that the corelet 100 programs. In one embodiment, thecorelet decomposer 215 outputs a flat JavaScript Object Notation (JSON)file that is suitable for use with cortical simulators.

FIG. 10 illustrates an example input mapping table 140, in accordancewith an embodiment of the invention. As noted, based on the inputmapping table 140 of a corelet 100, each input 120 received by thecorelet 100 is mapped to an input of a sub-corelet 110 within thecorelet 100. In one embodiment, the input mapping table 140 is anI-address routing table that maintains routing information for eachreceived input 120. The input mapping table 140 comprises multipleentries 141, wherein each entry 141 corresponds to an input 120 of thecorelet 100. Each entry 141 identifies an input of a sub-corelet 110within the corelet 100 to which a corresponding input 120 should berouted. For example, as shown in FIG. 10, Input₀ received by a corelet100 is routed to an input of a sub-corelet SC₁ of the corelet 100.

In one embodiment, the inputs 120 received by a corelet 100 are dividedinto multiple groups 142 of inputs 120, wherein each group 142 comprisesat least one input 120. Each group 142 of inputs 120 may be furtherdivided into multiple sub-groups of inputs 120.

FIG. 11 illustrates an example output mapping table 150, in accordancewith an embodiment of the invention. In one embodiment, the outputmapping table 150 of a corelet 100 is a routing table that maintainsrouting information for each output generated by each sub-corelet 110 ofthe corelet 100. The output mapping table 150 comprises multiple entries151, wherein each entry 151 corresponds to an output of a sub-corelet110 within the corelet 100. Each entry 151 identifies where acorresponding output generated by a sub-corelet 110 of the corelet 100should be routed to.

In one embodiment, each output generated by a sub-corelet 110 of thecorelet 100 is mapped to one of the following: an input of a sub-corelet110 within the corelet 100, or an output 130 of the corelet 100. Asstated above, each output 130 of the corelet 100 is routed to anothercorelet 100 or a motor unit 230. For example, as shown in FIG. 11,Output₁ generated by sub-corelet SC₀ of a corelet 100 is routed to aninput of the sub-corelet SC₁. As another example, Output₁ generated bysub-corelet SC₁ of the corelet 100 is mapped to Output₁, an output 130of the corelet 100.

In one embodiment, the outputs 130 generated by a corelet 100 aredivided into multiple groups 152 of outputs 130, wherein each group 152comprises at least one output 130. Each group 152 of outputs 130 may befurther divided into multiple sub-groups of outputs 130.

In one embodiment, a group 152 of outputs 130 from a corelet 100 may bemapped to a group 142 of inputs 120 received by another corelet 100.

FIG. 12 illustrates a flowchart of an example process 400 forprogramming a neural network, in accordance with an embodiment of theinvention. In process block 401, construct a corelet, wherein thecorelet comprises one or more constituent sub-corelets. In process block402, each input received by the corelet is mapped to an input of aconstituent sub-corelet. In process block 403, each output generated bya constituent sub-corelet is mapped to either an input of a constituentsub-corelet or an output of the corelet. In process block 404, at leastone neural core circuit of a neural network circuit is programmed withthe corelet.

FIG. 13 is a high level block diagram showing an information processingsystem 300 useful for implementing one embodiment of the presentinvention. The computer system includes one or more processors, such asprocessor 302. The processor 302 is connected to a communicationinfrastructure 304 (e.g., a communications bus, cross-over bar, ornetwork).

The computer system can include a display interface 306 that forwardsgraphics, text, and other data from the communication infrastructure 304(or from a frame buffer not shown) for display on a display unit 308.The computer system also includes a main memory 310, preferably randomaccess memory (RAM), and may also include a secondary memory 312. Thesecondary memory 312 may include, for example, a hard disk drive 314and/or a removable storage drive 316, representing, for example, afloppy disk drive, a magnetic tape drive, or an optical disk drive. Theremovable storage drive 316 reads from and/or writes to a removablestorage unit 318 in a manner well known to those having ordinary skillin the art. Removable storage unit 318 represents, for example, a floppydisk, a compact disc, a magnetic tape, or an optical disk, etc. which isread by and written to by removable storage drive 316. As will beappreciated, the removable storage unit 318 includes a computer readablemedium having stored therein computer software and/or data.

In alternative embodiments, the secondary memory 312 may include othersimilar means for allowing computer programs or other instructions to beloaded into the computer system. Such means may include, for example, aremovable storage unit 320 and an interface 322. Examples of such meansmay include a program package and package interface (such as that foundin video game devices), a removable memory chip (such as an EPROM, orPROM) and associated socket, and other removable storage units 320 andinterfaces 322 which allow software and data to be transferred from theremovable storage unit 320 to the computer system.

The computer system may also include a communication interface 324.Communication interface 324 allows software and data to be transferredbetween the computer system and external devices. Examples ofcommunication interface 324 may include a modem, a network interface(such as an Ethernet card), a communication port, or a PCMCIA slot andcard, etc. Software and data transferred via communication interface 324are in the form of signals which may be, for example, electronic,electromagnetic, optical, or other signals capable of being received bycommunication interface 324. These signals are provided to communicationinterface 324 via a communication path (i.e., channel) 326. Thiscommunication path 326 carries signals and may be implemented using wireor cable, fiber optics, a phone line, a cellular phone link, an RF link,and/or other communication channels.

In this document, the terms “computer program medium,” “computer usablemedium,” and “computer readable medium” are used to generally refer tomedia such as main memory 310 and secondary memory 312, removablestorage drive 316, and a hard disk installed in hard disk drive 314.

Computer programs (also called computer control logic) are stored inmain memory 310 and/or secondary memory 312. Computer programs may alsobe received via communication interface 324. Such computer programs,when run, enable the computer system to perform the features of thepresent invention as discussed herein. In particular, the computerprograms, when run, enable the processor 302 to perform the features ofthe computer system. Accordingly, such computer programs representcontrollers of the computer system.

From the above description, it can be seen that the present inventionprovides a system, computer program product, and method for implementingthe embodiments of the invention. The present invention further providesa non-transitory computer-useable storage medium for hierarchicalrouting and two-way information flow with structural plasticity inneural networks. The non-transitory computer-useable storage medium hasa computer-readable program, wherein the program upon being processed ona computer causes the computer to implement the steps of the presentinvention according to the embodiments described herein. References inthe claims to an element in the singular is not intended to mean “oneand only” unless explicitly so stated, but rather “one or more.” Allstructural and functional equivalents to the elements of theabove-described exemplary embodiment that are currently known or latercome to be known to those of ordinary skill in the art are intended tobe encompassed by the present claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. section 112, sixthparagraph, unless the element is expressly recited using the phrase“means for” or “step for.”

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A method comprising: generating a plurality ofmodular, reusable, scalable configurations, wherein each configurationcomprises a configuration file corresponding to a portion of a neuralnetwork, and the configuration file comprises a cost of utilizing theconfiguration to program the corresponding portion, an input mappingtable including addresses for routing each incoming firing event andsensory input received by the corresponding portion to one or more unitswithin the corresponding portion, an output mapping table includingaddresses of another portion of the neural network, a motor unit, and atleast one unit within the corresponding portion for routing eachoutgoing firing event generated by the corresponding portion, and afunction performed by the corresponding portion; combining at least twoof the configurations into a hierarchical arrangement; and programming amulti-core circuit chip structure based on the hierarchical arrangementto simulate a plurality of interconnected neurosynaptic core circuitsconfigured to perform a visual processing task.
 2. The method of claim1, wherein each neurosynaptic core circuit comprises a plurality ofelectronic synapses interconnecting a plurality of electronic neuronswith a plurality of electronic axons.
 3. The method of claim 1, whereineach configuration file corresponds to one of a portion of aneurosynaptic core circuit a neurosynaptic core circuit.
 4. The methodof claim 1, wherein each configuration file is a static configurationfile.
 5. The method of claim 1, wherein the visual processing task isone of edge detection, motion history tracking, or objectclassification.
 6. A system comprising a computer processor, acomputer-readable hardware storage medium, and program code embodiedwith the computer-readable hardware storage medium for execution by thecomputer processor to implement a method comprising: generating aplurality of modular, reusable, scalable configurations, wherein eachconfiguration comprises a configuration file corresponding to a portionof a neural network, and the configuration file comprises a cost ofutilizing the configuration to program the corresponding portion, aninput mapping table including addresses for routing each incoming firingevent and sensory input received by the corresponding portion to one ormore units within the corresponding portion, an output mapping tableincluding addresses of another portion of the neural network, a motorunit, and at least one unit within the corresponding portion for routingeach outgoing firing event generated by the corresponding portion, and afunction performed by the corresponding portion; combining at least twoof the configurations into a hierarchical arrangement; and programming amulti-core circuit chip structure based on the hierarchical arrangementto simulate a plurality of interconnected neurosynaptic core circuitsconfigured to perform a visual processing task.
 7. The system of claim6, wherein each neurosynaptic core circuit comprises a plurality ofelectronic synapses interconnecting a plurality of electronic neuronswith a plurality of electronic axons.
 8. The system of claim 6, whereineach configuration file corresponds to one of a portion of aneurosynaptic core circuit a neurosynaptic core circuit.
 9. The systemof claim 6, wherein each configuration file is a static configurationfile.
 10. The system of claim 6, wherein the visual processing task isone of edge detection, motion history tracking, or objectclassification.
 11. A computer program product comprising anon-transitory computer-useable storage medium having program codeembodied therewith, the program code being executable by a computer toimplement a method comprising: generating a plurality of modular,reusable, scalable configurations, wherein each configuration comprisesa configuration file corresponding to a portion of a neural network, andthe configuration file comprises a cost of utilizing the configurationto program the corresponding portion, an input mapping table includingaddresses for routing each incoming firing event and sensory inputreceived by the corresponding portion to one or more units within thecorresponding portion, an output mapping table including addresses ofanother portion of the neural network, a motor unit, and at least oneunit within the corresponding portion for routing each outgoing firingevent generated by the corresponding portion, and a function performedby the corresponding portion; combining at least two of theconfigurations into a hierarchical arrangement; and programming amulti-core circuit chip structure based on the hierarchical arrangementto simulate a plurality of interconnected neurosynaptic core circuitsconfigured to perform a visual processing task.
 12. The computer programproduct of claim 11, wherein each neurosynaptic core circuit comprises aplurality of electronic synapses interconnecting a plurality ofelectronic neurons with a plurality of electronic axons.
 13. Thecomputer program product of claim 11, wherein each configuration filecorresponds to one of a portion of a neurosynaptic core circuit aneurosynaptic core circuit.
 14. The computer program product of claim11, wherein each configuration file is a static configuration file. 15.The computer program product of claim 11, wherein the visual processingtask is one of edge detection, motion history tracking, or objectclassification.